CVE-2021-31356

Authenticated shell command execution via wrapper scripts

Published Oct 19, 2021 · Updated Sep 16, 2024

Command injection in Juniper Networks Junos OS Evolved before 20.4R3-S1-EVO, 21.1-EVO, and 21.2-EVO allows local users to run shell commands. The affected EVO UI wrapper scripts fail to neutralize command syntax in crafted CLI input before passing it to shell command processing. Authenticated CLI access is required; exploitation bypasses assigned command restrictions but does not raise the user's configured privilege level.

CVSS severity7.8
High
EPSS probability0.87%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Command injection in Juniper Networks Junos OS Evolved before 20.4R3-S1-EVO, 21.1-EVO, and 21.2-EVO allows local users to run shell commands. The affected EVO UI wrapper scripts fail to neutralize command syntax in crafted CLI input before passing it to shell command processing. Authenticated CLI access is required; exploitation bypasses assigned command restrictions but does not raise the user's configured privilege level.

The record

CVE
CVE-2021-31356
Published
Oct 19, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS Evolved
Classifications
CWE-77, T1059.004, T1059.008
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 19, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=21.1R1-EVO <21.1*
  2. Affected versionversion=21.2R1-EVO <21.2*
  3. Affected versionversion=unspecified <20.4R3-S1-EVO

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Juniper Networks · Junos OS Evolvedversion=21.1R1-EVO <21.1*; version=21.2R1-EVO <21.2*; version=unspecified <20.4R3-S1-EVO

Published CVSS scores

7.8Juniper NetworksCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-77Improper Neutralization of Special Elements used in a Command ('Command Injection')
T1059.004Command and Scripting Interpreter: Unix Shell
T1059.008Command and Scripting Interpreter: Network Device CLI

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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